Acoustic wave resonator with multiple resonant frequencies

ABSTRACT

Aspects of this disclosure relate to an acoustic wave resonator having at least two resonant frequencies. An acoustic wave filter can include series acoustic wave resonators and shunt acoustic wave resonators together arranged to filter a radio frequency signal. A first shunt resonator of the shunt acoustic wave resonators can include an interdigital transducer electrode and have at least a first resonant frequency and a second resonant frequency. Related acoustic wave resonators, multiplexers, wireless devices, and methods are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet, or any correction thereto,are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND Technical Field

Embodiments of this disclosure relate to acoustic wave resonators withtwo or more resonant frequencies.

Description of Related Technology

An acoustic wave filter can include a plurality of resonators arrangedto filter a radio frequency signal. Example acoustic wave filtersinclude surface acoustic wave (SAW) filters and bulk acoustic wave (BAW)filters. A surface acoustic wave resonator can include an interdigitaltransductor electrode on a piezoelectric substrate. The surface acousticwave resonator can generate a surface acoustic wave on a surface of thepiezoelectric layer on which the interdigital transductor electrode isdisposed.

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. An acoustic wave filtercan be a band pass filter. A plurality of acoustic wave filters can bearranged as a multiplexer. For example, two acoustic wave filters can bearranged as a duplexer. An acoustic wave filter with rejection over arelatively wide frequency range outside of a passband can be desirable.Designing such a filter can be challenging.

SUMMARY

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

One aspect of this disclosure is an acoustic wave filter configured tofilter a radio frequency signal. The acoustic wave filter includes shuntacoustic wave resonators including a first shunt acoustic waveresonator. The first shunt acoustic wave resonator includes aninterdigital transducer electrode. The first shunt acoustic resonatorhas at least a first resonant frequency and a second resonant frequency.The acoustic wave filter includes series acoustic wave resonators. Theseries acoustic wave resonators and the shunt acoustic wave resonatorsare together arranged to filter a radio frequency signal.

The acoustic wave filter can be a band pass filter having a pass band.The second resonant frequency can be between the first resonantfrequency and an edge of the pass band. The second resonant frequencycan be at least 5 megahertz above the first resonant frequency.

The interdigital transducer electrode can include first interdigitaltransducer electrode fingers having a first pitch corresponding to thefirst resonant frequency, and the interdigital transducer electrode caninclude second interdigital transducer electrode fingers having a secondpitch corresponding to the second resonant frequency.

The first shunt acoustic wave resonator can be a surface acoustic waveresonator. The first shunt acoustic wave resonator can be a temperaturecompensated surface acoustic wave resonator. The first shunt acousticwave resonator can be a multilayer piezoelectric substrate surfaceacoustic wave resonator. The first shunt acoustic wave resonator can bea Lamb wave resonator. The first shunt acoustic wave resonator can be aboundary acoustic wave resonator.

The first shunt acoustic wave resonator can have a third resonantfrequency.

The shunt acoustic wave resonators can include a second shunt acousticwave resonator having a plurality of resonant frequencies.

Another aspect of this disclosure is a multiplexer with filters forfiltering radio frequency signals. The multiplexer includes a firstfilter including series acoustic wave resonators and shunt acoustic waveresonators together arranged to filter a first radio frequency signal.The shunt acoustic wave resonators include a first shunt acoustic waveresonator. The first shunt resonator includes an interdigital transducerelectrode. The first shunt acoustic wave resonator has a plurality ofresonant frequencies. The multiplexer also includes a second filtercoupled to the first filter at a common node. The second filter isconfigured to filter a second radio frequency signal.

The interdigital transducer electrode can include first interdigitaltransducer electrode fingers having a first pitch corresponding to thefirst resonant frequency, and the interdigital transducer electrode caninclude second interdigital transducer electrode fingers having a secondpitch corresponding to the second resonant frequency.

The second filter can include second series acoustic wave resonators andsecond shunt acoustic wave resonators. The second shunt acoustic waveresonators can include a second shunt acoustic wave resonator having atleast two resonant frequencies.

The multiplexer can further include: a third filter coupled to thecommon node, the third filter configured to filter a third radiofrequency signal; and a fourth filter coupled to the common node, thefourth filter configured to filter a fourth radio frequency signal. Themultiplexer can provide filtering for at least two carriers of a carrieraggregation. Each filter of the multiplexer can be an acoustic wavefilter.

The first shunt acoustic wave resonator can include any suitablecombination of features of the acoustic wave resonators having two ormore resonant frequencies disclosed herein.

The second filter can include an acoustic wave resonator that includesany suitable combination of features of the acoustic wave resonatorshaving two or more resonant frequencies disclosed herein.

Another aspect of this disclosure is a method of filtering a radiofrequency signal with an acoustic wave filter. The method includes:receiving, by an acoustic wave filter, a radio frequency signal; andgenerating, by a shunt acoustic wave resonator including an interdigitaltransducer electrode and being included in the acoustic wave filter, aplurality of notches in a frequency response of the shunt acoustic waveresonator to thereby improve rejection of the acoustic wave filter.

The interdigital transducer electrode can include first interdigitaltransducer electrode fingers having a first pitch corresponding to afirst resonant frequency that creates a first notch of the plurality ofnotches, and the interdigital transducer electrode can include secondinterdigital transducer electrode fingers having a second pitchcorresponding to a second resonant frequency that creates a second notchof the plurality of notches. The acoustic wave filter can be a band passfilter having a pass band. The second resonant frequency can be betweenthe first resonant frequency and a lower edge of the pass band. Theacoustic wave filter can include any suitable combination of features ofthe acoustic wave filters disclosed herein.

Another aspect of this disclosure is an acoustic wave filter configuredto filter a radio frequency signal. The acoustic wave filter includesshunt acoustic wave resonators including a first shunt acoustic waveresonator. The first shunt acoustic wave resonator has at least a firstresonant frequency and a second resonant frequency. The acoustic wavefilter includes series acoustic wave resonators. The series acousticwave resonators and the shunt acoustic wave resonators are togetherarranged to filter a radio frequency signal.

Another aspect of this disclosure is an acoustic wave resonator with aplurality of resonant frequencies. The acoustic wave resonator includesa piezoelectric layer and an interdigital transducer electrode on thepiezoelectric layer. The interdigital transducer electrode includesfirst interdigital transducer electrode fingers and second interdigitaltransducer electrode fingers. The first interdigital transducerelectrode fingers have a first pitch corresponding to a first resonantfrequency. The second interdigital transducer electrode fingers having asecond pitch corresponding to a second resonant frequency.

The second resonant frequency can be between the first resonantfrequency and an edge of a pass band of an acoustic wave filter thatincludes the acoustic wave resonator. The edge can be a lower edge ofthe passband.

The acoustic wave resonator can be configured to generate a surfaceacoustic wave.

The acoustic wave resonator can further include a temperaturecompensation layer over the interdigital transducer electrode. Thetemperature compensation layer can be a silicon dioxide layer.

The acoustic wave resonator can further include a support substrate, inwhich the piezoelectric layer is positioned on the support substrate.

The acoustic wave resonator can be configured to generate a boundaryacoustic wave.

The acoustic wave resonator can be configured to generate a Lamb wave.

The interdigital transducer electrode can include third interdigitaltransducer electrode fingers having a third pitch corresponding to athird resonant frequency of the acoustic wave resonator.

The second resonant frequency can be at least 5 megahertz above thefirst resonant frequency. The second resonant frequency can be betweenthe first resonant frequency and an edge of a passband of a filter thatincludes the acoustic wave resonator. The edge can be a lower edge ofthe passband.

The piezoelectric layer can be a lithium niobate layer. Thepiezoelectric layer can be a lithium tantalate layer. The piezoelectriclayer can be an aluminum nitride layer.

The interdigital transducer electrode can include a bus bar from whichboth the first interdigital transducer electrode fingers and the secondinterdigital transducer electrode fingers extend. The interdigitaltransducer electrode can be positioned between two acoustic reflectorsthat are on the piezoelectric layer.

Another aspect of this disclosure is an acoustic wave filter configuredto filter a radio frequency signal. The acoustic wave filter includes aplurality of acoustic wave resonators. The plurality of acoustic waveresonators include a shunt acoustic wave resonator that includes apiezoelectric layer and an interdigital transducer electrode on thepiezoelectric layer. The interdigital transducer electrode includesfirst interdigital transducer electrode fingers and second interdigitaltransducer electrode fingers. The first interdigital transducerelectrode fingers have a first pitch corresponding to a first resonantfrequency. The second interdigital transducer electrode fingers have asecond pitch corresponding to a second resonant frequency.

The shunt acoustic wave resonator can one or more suitable featuresadditional features of any of the acoustic wave resonators disclosedherein.

Another aspect of this disclosure is a multiplexer with filters forfiltering radio frequency signals. The multiplexer includes: a firstfilter including a shunt acoustic wave resonator, the shunt acousticwave resonator including a piezoelectric layer and an interdigitaltransducer electrode on the piezoelectric layer, the interdigitaltransducer electrode including first interdigital transducer electrodefingers and second interdigital transducer electrode fingers, the firstinterdigital transducer electrode fingers having a first pitchcorresponding to a first resonant frequency, and the second interdigitaltransducer electrode fingers having a second pitch corresponding to asecond resonant frequency; and a second filter coupled to the firstfilter at a common node, the second filter configured to filter a secondradio frequency signal.

The second filter can include acoustic wave resonators.

The multiplexer can further include: a third filter coupled to thecommon node, the third filter configured to filter a third radiofrequency signal; and a fourth filter coupled to the common node, thefourth filter configured to filter a fourth radio frequency signal. Eachof the second filter, the third filter, and the fourth filter can be anacoustic wave filter. The multiplexer can be configured to providefiltering for at least two carriers of a carrier aggregation.

The shunt acoustic wave resonator can include one or more suitablefeatures of any of the acoustic wave resonators disclosed herein.

Another aspect of this disclosure is a method of filtering a radiofrequency signal with an acoustic wave filter. The method includes:receiving, by an acoustic wave filter, a radio frequency signal; andgenerating, by a shunt acoustic wave resonator of the acoustic wavefilter that includes an interdigital transducer electrode includingfirst interdigital transducer electrode fingers having a first pitch andsecond interdigital transducer electrode fingers having a second pitch,two notches in a frequency response of the shunt acoustic wave resonatorcorresponding to the first pitch and the second pitch to thereby improverejection of the acoustic wave filter.

The shunt acoustic wave resonator can include one or more suitablefeatures of any of the acoustic wave resonators disclosed herein.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 is a diagram of an acoustic wave resonator with interdigitaltransducer (IDT) electrode with two different pitches between IDTfingers according to an embodiment.

FIG. 2A is a graph of conductance for a surface acoustic wave (SAW)resonator with the IDT of FIG. 1 .

FIG. 2B is a graph of a frequency response for a SAW resonator with theIDT of FIG. 1 .

FIG. 3A is a graph of a frequency response of individual shuntresonators and a SAW filter that includes the resonators.

FIG. 3B is a graph of a frequency response of one shunt resonator and aSAW filter that includes the shunt resonator.

FIG. 3C is a graph of a frequency response of individual shuntresonators and a SAW filter with one shunt resonator having an IDTelectrode similar to FIG. 1 according to an embodiment.

FIG. 3D is a graph of a frequency response of a shunt resonator havingan IDT electrode similar to FIG. 1 and a SAW filter that includes theshunt resonator according to an embodiment.

FIG. 4 is a diagram of a cross section of a SAW resonator according toan embodiment.

FIG. 5 is a diagram of a cross section of a temperature compensated SAWresonator according to an embodiment.

FIG. 6 is a diagram of a cross section of a multilayer piezoelectricsubstrate SAW resonator according to an embodiment.

FIG. 7 is a diagram of a cross section of a boundary wave resonatoraccording to an embodiment.

FIG. 8 is a diagram of a cross section of a Lamb wave resonatoraccording to an embodiment.

FIG. 9 is a diagram of a cross section of a solidly mounted Lamb waveresonator according to an embodiment.

FIG. 10 is a diagram of an acoustic wave resonator with an IDT electrodewith three different pitches between IDT fingers according to anembodiment.

FIG. 11 is a schematic diagram of a ladder filter that includes a shuntresonator according to an embodiment.

FIG. 12 is a schematic diagram of a lattice filter that includes aresonator according to an embodiment.

FIG. 13A is a schematic diagram of a duplexer according to anembodiment.

FIG. 13B is a schematic diagram of a cross section of surface acousticwave resonators of the duplexer of FIG. 13A according to an embodiment.

FIG. 14A is a schematic diagram of a duplexer that includes an acousticwave filter according to an embodiment.

FIG. 14B is a schematic diagram of a multiplexer that includes anacoustic wave filter according to an embodiment.

FIG. 15 is a schematic diagram of a radio frequency module that includesan acoustic wave filter according to an embodiment.

FIG. 16 is a schematic block diagram of a module that includes anantenna switch and duplexers according to an embodiment.

FIG. 17 is a schematic block diagram of a module that includes a poweramplifier, a radio frequency switch, and duplexers according to anembodiment.

FIG. 18 is a schematic diagram of a radio frequency module that includesan acoustic wave filter according to an embodiment.

FIG. 19A is a schematic block diagram of a wireless communication devicethat includes an acoustic wave filter according to an embodiment.

FIG. 19B is a schematic block diagram of another wireless communicationdevice that includes an acoustic wave filter according to an embodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents variousdescriptions of specific embodiments. However, the innovations describedherein can be embodied in a multitude of different ways, for example, asdefined and covered by the claims. In this description, reference ismade to the drawings where like reference numerals can indicateidentical or functionally similar elements. It will be understood thatelements illustrated in the figures are not necessarily drawn to scale.Moreover, it will be understood that certain embodiments can includemore elements than illustrated in a drawing and/or a subset of theelements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

Filters with rejection over a relatively wide frequency range aredesired for certain radio frequency (RF) systems. Acoustic wave filterscan include series acoustic wave resonators and shunt acoustic waveresonators. An anti-resonance frequency of a series acoustic waveresonator can be used for rejection in an acoustic wave filter. Theanti-resonance frequency of the series acoustic wave resonator cancreate an open to thereby create a notch in a frequency response. Aresonant frequency of a shunt acoustic wave resonator can be used forrejection in an acoustic wave filter. The resonant frequency of theshunt acoustic wave resonator can create a short to ground to therebycreate a notch in a frequency response. The series acoustic waveresonator can have its highest conductance at the resonant frequency.

To achieve a relatively wide frequency range for rejection, an acousticwave filter can include a plurality of shunt acoustic wave resonatorseach having a different resonant frequency. As an example, an acousticwave filter can include 4 or 5 shunt acoustic wave resonators eachhaving different respective resonant frequencies. With more shuntacoustic wave resonators having different resonant frequencies, theacoustic wave filter can achieve relatively higher rejection. At thesame time, an acoustic wave filter with more acoustic wave resonatorscan consume additional area.

Aspects of this disclosure relate to an acoustic wave resonator havingat least two resonant frequencies. The acoustic wave resonator can bearranged as a shunt resonator in an acoustic wave filter. Such a shuntresonator can achieve at least two notches and increase a frequencyrange for rejection of the acoustic wave filter. The acoustic wavefilter can be a band pass filter with a pass band. The acoustic waveresonator can have a second resonant frequency between a first resonantfrequency and a lower edge of the pass band.

An acoustic wave resonator with at least two resonant frequencies caninclude an interdigital transducer (IDT) electrode with first IDTfingers having a first pitch corresponding to a first resonant frequencyand second IDT fingers having a second pitch corresponding to a secondresonant frequency. The acoustic wave resonator can be a surfaceacoustic wave (SAW) resonator. For example, the acoustic wave resonatorcan be a temperature compensated SAW resonator, a non-temperaturecompensated SAW resonator, or a multilayer piezoelectric substrate SAWresonator. Other types of acoustic wave resonators with an IDT electrodehaving at least two pitches corresponding to two resonant frequenciesare disclosed, such as boundary wave resonators and Lamb waveresonators.

A shunt acoustic wave resonator with multiple resonant frequencies canimprove out of band rejection for a filter without significantlydegrading the filter response in a pass band. With a shunt acoustic waveresonator with multiple resonant frequencies, stringent rejectionspecifications can be met with fewer acoustic wave resonators than someprevious solutions.

FIG. 1 is a diagram of an acoustic wave resonator 10 with an IDTelectrode 11 with two different pitches between IDT fingers according toan embodiment. The acoustic wave resonator 10 is shown in plan view. Theacoustic wave resonator 10 can be a SAW resonator in certainembodiments. As illustrated, the acoustic wave resonator 10 includes anIDT electrode 11 including a bus bar 12, first IDT fingers 14A, secondIDT fingers 14B, a first acoustic reflector 16, and a second acousticreflector 18. The IDT electrode 11 and the acoustic reflectors 16 and 18can be positioned on a piezoelectric layer. The acoustic reflectors 16and 18 are separated from the IDT electrode 12 by respective gaps.

The IDT electrode 11 is positioned between the first acoustic reflector16 and the second acoustic reflector 18. The IDT electrode 11 includes abus bar 12 and IDT fingers 14A and 14B extending from the bus bar 12. InRegion 1 of the acoustic wave resonator 10, the first IDT fingers 14Ahave a pitch of λ1. The acoustic wave resonator 10 can include anysuitable number of first IDT fingers 14A. The pitch λ1 of the first IDTfingers 14A corresponds to a first resonant frequency. In Region 2 ofthe acoustic wave resonator 10, the second IDT fingers 14B have a pitchof λ2. The acoustic wave resonator 10 can include any suitable number ofsecond IDT fingers 14B. The pitch λ2 of the second IDT fingers 14Bcorresponds to a second resonant frequency. Accordingly, the acousticwave resonator 10 has IDT fingers with two different pitches thatcorrespond to two different resonant frequencies.

FIG. 2A is a graph of conductance for a SAW resonator with the IDT 11 ofFIG. 1 . As shown in FIG. 2A, the conductance graph has peaks at twofrequencies f1 and f2. The frequencies f1 and f2 correspond to thepitches λ1 and λ2, respectively, of the IDT 11 of FIG. 1 . The firstresonant frequency f1 is distinct from the second resonant frequency f2.In certain instances, the second resonant frequency f2 is at least 5megahertz (MHz) above the first resonant frequency f1. The secondresonant frequency f2 can also be between the first resonant frequencyf1 and a lower edge of a pass band of a filter that includes the SAWresonator.

FIG. 2B is a graph of a frequency response for a SAW resonator with theIDT 11 of FIG. 1 . The SAW resonator is arranged as a shunt resonator.The two notches in the frequency response shown in FIG. 2B are at theresonant frequencies f1 and f2 shown in FIG. 2A. The two notches can bereferred to as rejection poles.

A shunt SAW resonator corresponding to the graphs of FIGS. 2A and 2B canhave two resonance peaks. For example, a shunt SAW resonator can havethe resonance peaks at resonant frequencies f1 and f2 are shown in FIG.2A. The shunt SAW resonator can be included in a band pass filter with apass band. The first resonant frequency f1 is below the second resonantfrequency f2. The second resonant frequency f2 can be below a lower edgeof the pass band of the band pass filter. With such a shunt SAWresonator, rejection below the pass band of the filter can be improved.

FIG. 3A is a graph of a frequency response of individual shuntresonators and a SAW ladder filter that includes the resonators. FIG. 3Aillustrates a ripple 302 in the frequency response of the SAW filterthat is above a rejection specification.

FIG. 3B is a graph of a frequency response of one shunt resonator and aSAW ladder filter that includes the shunt resonator. The graph of theone shunt resonator that can contribute most to the ripple 302 in thefrequency response of the SAW filter is shown in FIG. 3B together withthe frequency response. The ripple 302 brings the frequency response ofthe SAW filter outside of the specification for out of band rejection.

FIG. 3C is a graph of a frequency response of individual shuntresonators and a SAW ladder filter with one shunt resonator having anIDT electrode similar to FIG. 1 according to an embodiment. The SAWfilter corresponding to FIGS. 3C and 3D has the topology of the filter132 of FIG. 13A. The SAW filter corresponding to the graph of FIG. 3C islike the SAW filter corresponding to the graph of FIG. 3A except thatthe SAW filter corresponding to the graph of FIG. 3C includes one shuntSAW resonator with an IDT electrode similar to the IDT electrode 11 ofFIG. 1 . As shown in FIG. 3C, the shunt resonator having an IDTelectrode similar to FIG. 1 can improve the out of band rejection of theSAW filter and bring the out of band rejection in compliance with thespecification in region 304 of the filter frequency response. As anexample, the SAW filter can be a receive filter and the graph of FIG. 3Ccan indicate an improvement in transmit band rejection relative to thegraph of FIG. 3A that includes the ripple 302 that violates thespecification.

FIG. 3D is a graph of a frequency response of a shunt resonator havingan IDT electrode similar to FIG. 1 and a SAW ladder filter that includesthe shunt resonator according to an embodiment. The shunt resonatorhaving an IDT electrode similar to FIG. 1 has the lowest resonantfrequency of the shunt resonators in the filter with the frequencyresponse shown in FIG. 3D. The shunt resonator having an IDT electrodesimilar to FIG. 1 has two notches in its frequency response as shown inFIG. 3D. The two notches for the shunt SAW resonator shown in FIG. 3Dare not as deep as the single notch for the corresponding resonator witha uniform IDT electrode finger pitch that is shown in FIG. 3B. A shuntresonator with a two resonant frequencies relatively far away from anedge of the passband of the filter that includes the shunt resonator canmeet performance specifications with the reduced depths of the notchesat the two resonant frequencies. The shunt SAW resonator with the IDTelectrode similar to FIG. 1 does not significantly degrade the pass bandof the filter and also improves the out of band rejection. The shunt SAWresonator with the IDT electrode similar to FIG. 1 can advantageouslyincrease the rejection frequency range without adding additionalcomponents, such as other resonators.

An acoustic wave resonator having multiple resonant frequencies can be aSAW resonator. Such a SAW resonator can include a piezoelectric layerand an IDT electrode on the piezoelectric layer. The IDT electrodeincludes first IDT fingers having a first pitch corresponding to a firstresonant frequency and second IDT fingers having a second pitchcorresponding to a second resonant frequency. Example SAW resonatorswill be discussed with reference to FIGS. 4 to 6 .

FIG. 4 is a diagram of a cross section of a SAW resonator 40 accordingto an embodiment. The SAW resonator 40 is an example of an acoustic waveresonator having multiple resonant frequencies. The SAW resonator 40 isan example of a non-temperature compensated SAW resonator. SAW filtersdisclosed herein can include any suitable number of SAW resonators 40.The illustrated SAW resonator 40 includes a piezoelectric layer 42 andan IDT electrode 44 on the piezoelectric layer 42. The piezoelectriclayer 42 can be a lithium niobate layer or a lithium tantalate layer,for example. As shown in FIG. 4 , the IDT electrode 44 includes firstIDT electrode fingers in Region 1 having a pitch of λ1 and second IDTelectrode fingers in Region 2 having a pitch of λ2. With differentpitches for the first and second IDT electrode fingers, the SAWresonator 40 can have two resonant frequencies. The two resonantfrequencies can correspond to two notches in the frequency response ofthe SAW resonator 40. The SAW resonator 40 can be included as a shuntresonator in a filter to improve out of band rejection.

FIG. 5 is a diagram of a cross section of a temperature compensated SAW(TCSAW) resonator 50 according to an embodiment. The TCSAW resonator 50is an example of an acoustic wave resonator having multiple resonantfrequencies. SAW filters disclosed herein can include any suitablenumber of TCSAW resonators 50. The illustrated TCSAW resonator 50includes a piezoelectric layer 42, an IDT electrode 44 on thepiezoelectric layer 42, and a temperature compensation layer 52 over theIDT electrode 44. The piezoelectric layer 42 can be a lithium niobatesubstrate or a lithium tantalate substrate, for example.

The temperature compensation layer 52 can bring the temperaturecoefficient of frequency (TCF) of the TCSAW resonator 50 closer to zerorelative to a similar SAW resonator without the temperature compensationlayer 52. The temperature compensation layer 52 can have a positive TCF.This can compensate for the piezoelectric layer 42 having a negativeTCF. The temperature compensation layer 52 can be a silicon dioxide(SiO₂) layer. The temperature compensation layer 52 can include anyother suitable temperature compensating material including withoutlimitation a tellurium dioxide (TeO₂) layer or a silicon oxyfluoride(SiOF layer). The temperature compensation layer 52 can include anysuitable combination of SiO₂, TeO₂, and/or SiOF.

As shown in FIG. 5 , the IDT electrode 44 includes first IDT electrodefingers in Region 1 having a pitch of λ1 and second IDT electrodefingers in Region 2 having a pitch of λ2. With different pitches for thefirst and second IDT electrode fingers, the TCSAW resonator 50 can havetwo resonant frequencies. The two resonant frequencies can correspond totwo notches in the frequency response of the TCSAW resonator 50. TheTCSAW resonator 50 can be included as a shunt resonator in a filter toimprove out of band rejection.

FIG. 6 is a diagram of a cross section of a multilayer piezoelectricsubstrate (MPS) SAW resonator 60 according to an embodiment. The MPS SAWresonator 60 is an example of an acoustic wave resonator having multipleresonant frequencies. SAW filters disclosed herein can include anysuitable number of MPS SAW resonators 60. The illustrated MPS SAWresonator 60 includes a multilayer piezoelectric substrate including apiezoelectric layer 42 and a support substrate 62. The MPS SAW resonator60 also includes an IDT electrode 44 on the piezoelectric layer 42.

The piezoelectric layer 42 can be a lithium niobate substrate or alithium tantalate substrate, for example. In certain instances, thepiezoelectric layer 42 can have a thickness of less than λ, in which λis a wavelength of a surface acoustic wave generated by the MPS SAWresonator 60. In some other instances, the piezoelectric layer 42 canhave a thickness on the order of 10 s of λ, in which λ is a wavelengthof a surface acoustic wave generated by the MPS SAW resonator 60. Thethickness of the piezoelectric layer 42 can be in a range from about 20microns to 30 microns in certain applications. The support substrate 62can be a silicon substrate, a quartz substrate, a sapphire substrate, apolycrystalline spinel substrate, or any other suitable carriersubstrate. As one example, the MPS SAW resonator 60 can include apiezoelectric substrate 42 that is lithium tantalate and a supportsubstrate 62 that is silicon.

In some instances, one or more additional layers can be included in themultilayer piezoelectric substrate of an MPS SAW resonator. Non-limitingexamples of a layer of the one or more additional layers include asilicon dioxide layer, a silicon nitride layer, an aluminum nitridelayer, an adhesion layer, a dispersion adjustment layer, and a thermaldissipation layer. As an illustrative example, a multilayerpiezoelectric substrate can include a lithium tantalate layer over asilicon dioxide layer over an aluminum nitride layer over a siliconlayer. As one more illustrative example, a multilayer piezoelectricsubstrate can include a lithium niobate layer over a silicon dioxidelayer over a high impedance layer, in which the high impedance layer hasa higher acoustic impedance than the lithium niobate layer.

As shown in FIG. 6 , the IDT electrode 44 includes first IDT electrodefingers in Region 1 having a pitch of λ1 and second IDT electrodefingers in Region 2 having a pitch of λ2. With different pitches for thefirst and second IDT electrode fingers, the MPS SAW resonator 60 canhave two resonant frequencies. The two resonant frequencies cancorrespond to two notches in the frequency response of the MPS SAWresonator 60. The MPS SAW resonator 60 can be included as a shuntresonator in a filter to improve out of band rejection.

Another type of acoustic wave resonator that can have multiple resonantfrequencies in accordance with any suitable principles and advantagesdisclosed herein is a boundary wave resonator. FIG. 7 is a diagram of across section of a boundary wave resonator 70 according to anembodiment. The boundary wave resonator 70 is an example of an acousticwave resonator having multiple resonant frequencies. Acoustic wavefilters disclosed herein can include any suitable number of boundarywave resonators 70. As illustrated, the boundary wave resonator 70includes a piezoelectric layer 42, an interdigital transducer electrode44 on the piezoelectric layer 42, high velocity layers 72 and 74 onopposing sides of the piezoelectric layer 42, and a low velocity layer76 positioned between the piezoelectric layer 42 and a first highvelocity layer 72 of the high velocity layers. The low velocity layer 76has a lower acoustic velocity than the high velocity layers 72 and 74,in which the acoustic velocity is the speed of sound of a shear wavepropagating in a solid. The boundary wave resonator 70 is configured togenerate a boundary acoustic wave such that acoustic energy isconcentrated at a boundary of the piezoelectric layer 42 and the lowvelocity layer 76. As one example, the low velocity layer 76 can be asilicon dioxide layer and the high velocity layers 72 and 74 can besilicon layers. As shown in FIG. 7 , the IDT electrode 44 includes firstIDT electrode fingers in Region 1 having a pitch of λ1 and second IDTelectrode fingers in Region 2 having a pitch of λ2. These differentpitches correspond to different resonant frequencies of the boundaryacoustic wave resonator 70.

An acoustic wave resonator having multiple resonant frequencies can be aLamb wave resonator. Example Lamb wave resonators will be discussed withreference to FIGS. 8 and 9 .

FIG. 8 is a diagram of a cross section of a Lamb wave resonator 80according to an embodiment. The Lamb wave resonator 80 is an example ofan acoustic wave resonator having multiple resonant frequencies.Acoustic wave filters disclosed herein can include any suitable numberof Lamb wave resonators 80. As illustrated, the Lamb wave resonator 80includes a piezoelectric layer 42, an interdigital transducer electrode44 on the piezoelectric layer 42, and an electrode 84. The piezoelectriclayer 42 can be a thin film. The piezoelectric layer 42 can be analuminum nitride layer. In other instances, the piezoelectric layer 42can be any suitable piezoelectric layer. For example, the piezoelectriclayer 42 can be a lithium niobate layer or a lithium tantalate layer.The electrode 84 and the IDT electrode 44 are on opposing sides of thepiezoelectric layer 42. The electrode 84 can be grounded in certaininstances. In some other instances, the electrode 84 can be floating. Anair cavity 85 is disposed between the electrode 84 and a substrate 82.Any suitable cavity can be implemented in place of the air cavity 85.The substrate 82 can be a semiconductor substrate. For example, thesubstrate 82 can be a silicon substrate. The substrate 82 can be anyother suitable substrate, such as a quartz substrate, a sapphiresubstrate, or a spinel substrate. As shown in FIG. 8 , the IDT electrode44 includes first IDT electrode fingers in Region 1 having a pitch of λ1and second IDT electrode fingers in Region 2 having a pitch of λ2. Thesedifferent pitches correspond to different resonant frequencies of theLamb wave resonator 80. Alternatively or additionally, thickness of thepiezoelectric layer 42 in the Lamb wave resonator 80 can be different inRegion 1 and Region 2 to cause a difference in resonant frequencybetween Region 1 and Region 2.

FIG. 9 is a diagram of a cross section of a solidly mounted Lamb waveresonator 90 according to an embodiment. The solidly mounted Lamb waveresonator 90 is an example of an acoustic wave resonator having multipleresonant frequencies. Acoustic wave filters disclosed herein can includeany suitable number of solidly mounted Lamb wave resonators 90. Asillustrated, the solidly mounted Lamb wave resonator 90 includes anelectrode 84, a piezoelectric layer 42, an IDT electrode 44 on thepiezoelectric layer 42, and a Bragg reflector 92 located between thesubstrate 82 and the electrode 84. The Bragg reflector 92 includesalternating low impedance and high impedance layers. As an example, theBragg reflector 92 can include alternating silicon dioxide layers andtungsten layers. Any other suitable Bragg reflector can alternatively oradditionally be included in the solidly mounted Lamb wave resonator 90.In the solidly mounted Lamb wave resonator 90, the piezoelectric layer42 can be an aluminum nitride layer, for example. As shown in FIG. 9 ,the IDT electrode 44 includes first IDT electrode fingers in Region 1having a pitch of λ1 and second IDT electrode fingers in Region 2 havinga pitch of λ2. These different pitches correspond to different resonantfrequencies of the solidly mounted Lamb wave resonator 90. Alternativelyor additionally, thickness of the piezoelectric layer 42 in the solidlymounted Lamb wave resonator 90 can be different in Region 1 and Region 2to cause a difference in resonant frequency between Region 1 and Region2.

Although embodiments disclosed herein relate to acoustic wave resonatorswith two resonant frequencies, any suitable principles and advantagesdisclosed herein can be implemented in an acoustic wave resonator havingthree or more resonant frequencies. With three or more resonantfrequencies, corresponding notches in the frequency response of anacoustic wave resonator can be less deep than for a similar acousticwave resonator with two resonant frequencies. Accordingly, such anacoustic wave resonator can be implemented in applications in which suchnotch depth can contribute to a specification for a frequency responseof a filter. An example IDT electrode for an acoustic wave resonatorhaving three resonant frequencies will be discussed with reference toFIG. 10 . An IDT electrode in an acoustic wave resonator with three ormore resonant frequencies can include a sufficient number of IDTelectrode fingers to provide a sufficiently high quality factor (Q) forparticular applications.

FIG. 10 is a diagram of an acoustic wave resonator 100 with an IDTelectrode 101 with three different pitches between IDT fingers accordingto an embodiment. The acoustic wave resonator 100 is shown in plan view.The acoustic wave resonator 100 can be a SAW resonator in certainembodiments. The IDT electrode 101 is similar to the IDT electrode 11 ofFIG. 1 except that the IDT electrode 101 additionally includes third IDTfingers 14C having a third pitch λ3. As illustrated, the acoustic waveresonator 100 includes an IDT electrode 101 including a bus bar 12 andIDT fingers 14A to 14C, a first acoustic reflector 16, and a secondacoustic reflector 18.

The IDT electrode 101 includes a bus bar 12 and IDT fingers 14A, 14B,and 14C extending from the bus bar 12. In Region 1 of the acoustic waveresonator 101, first IDT fingers 14A have a pitch of λ1. The acousticwave resonator 100 can include any suitable number of first IDT fingers14A. The pitch λ1 of the first IDT fingers 14A corresponds to a firstresonant frequency. In Region 2 of the acoustic wave resonator 100,second IDT fingers 14B have a pitch of λ2. The acoustic wave resonator100 can include any suitable number of second IDT fingers 14B. The pitchλ2 of the second IDT fingers 14B corresponds to a second resonantfrequency. In Region 3 of the acoustic wave resonator 100, third IDTfingers 14C have a pitch of λ3. The acoustic wave resonator 100 caninclude any suitable number of third IDT fingers 14C. The pitch λ3 ofthe third IDT fingers 14C corresponds to a third resonant frequency.Accordingly, the acoustic wave resonator 100 has IDT fingers with threedifferent pitches that correspond to three different resonantfrequencies.

Acoustic wave resonators having multiple resonant frequencies can beimplemented in a variety of different filters. Example filters includewithout limitation notch filters with notches created by the resonantfrequencies of shunt resonator(s), ladder filters, lattice filters, andhybrid filters that use shunt resonator resonant frequencies forrejection.

One or more acoustic wave resonators including any suitable combinationof features disclosed herein be included in a filter arranged to filtera radio frequency signal in a fifth generation (5G) New Radio (NR)operating band within Frequency Range 1 (FR1). A filter arranged tofilter a radio frequency signal in a 5G NR operating band can includeone or more SAW resonators disclosed herein. FR1 can be from 410megahertz (MHz) to 7.125 gigahertz (GHz), for example, as specified in acurrent 5G NR specification. One or more acoustic wave resonators inaccordance with any suitable principles and advantages disclosed hereincan be included in a filter arranged to filter a radio frequency signalin a fourth generation (4G) Long Term Evolution (LTE) operating band.One or more acoustic wave resonators in accordance with any suitableprinciples and advantages disclosed herein can be included in a filterhaving a passband that includes a 4G LTE operating band and a 5G NRoperating band.

Acoustic wave filters disclosed herein can have a ladder filtertopology. FIG. 11 is a schematic diagram of a ladder filter 110 thatincludes a shunt resonator according to an embodiment. The ladder filter110 is an example topology of a band pass filter formed from acousticwave resonators. In a band pass filter with a ladder filter topology,the shunt resonators can have lower resonant frequencies than the seriesresonators. The ladder filter 110 can be arranged to filter an RFsignal. As illustrated, the ladder filter 110 includes series acousticwave resonators 111, 113, 115, 117, and 119 and shunt acoustic waveresonators 112, 114, 116, and 118 coupled between an RF port RF and anantenna port ANT. The acoustic wave resonators of the ladder filter 110can include any suitable acoustic wave resonators. The RF port can be atransmit port for a transmit filter or a receive port for a receivefilter. Any suitable number of series acoustic wave resonators can be inincluded in a ladder filter. Any suitable number of shunt acoustic waveresonators can be included in a ladder filter. Any of the illustratedshunt acoustic wave resonators 112, 114, 116, and 118 can have multipleresonant frequencies in accordance with any suitable principles andadvantages disclosed herein. In certain instances, a single shuntresonator of the ladder filter 110 has multiple resonant frequencies inaccordance with any suitable principles and advantages disclosed herein.In some other instances, two or more shunt resonators of the ladderfilter 110 can have multiple resonant frequencies in accordance with anysuitable principles and advantages disclosed herein.

Acoustic wave filters disclosed herein can have a lattice filtertopology. FIG. 12 is a schematic diagram of a lattice filter 120 thatincludes a resonator according to an embodiment. The lattice filter 120is an example topology of a band pass filter formed from acoustic waveresonators. The lattice filter 120 can be arranged to filter an RFsignal. As illustrated, the lattice filter 120 includes acoustic waveresonators 122, 124, 126, and 128. The acoustic wave resonators 122 and124 are considered series resonators. The acoustic wave resonators 126and 128 are considered shunt resonators. The illustrated lattice filter120 has a balanced input and a balanced output. The illustrated acousticwave resonators 126 and/or 128 can have multiple resonant frequencies inaccordance with any suitable principles and advantages disclosed herein.

In some instances, an acoustic wave filter that includes a shuntresonator having two or more resonant frequencies can have a topologythat is a hybrid of a ladder filter and a lattice filter. According tocertain applications, an acoustic wave shunt resonator having two ormore resonant frequencies can be included in filter that also includesone or more inductors and one or more capacitors.

FIG. 13A is a schematic diagram of a duplexer 130 according to anembodiment. The duplexer 130 includes a first filter 132 and a secondfilter 134 coupled together at an antenna node ANT. The antenna node ANTis a common node of the duplexer 130. A shunt inductor L1 is alsocoupled to the first filter 132 and 134 at the antenna node ANT. Theduplexer 130 can be a diversity receive duplexer in which the firstfilter 132 is a receive filter and the second filter 134 is a receivefilter. As an illustrative example, the first filter 132 can be a Band 3receive filter and the second filter 134 can be a Band 66 receivefilter.

The first filter 132 includes a plurality of acoustic wave resonators.As illustrated, the first filter 132 is a ladder filter. The acousticwave resonators of the first filter 132 include series resonators RA1,RA3, RA5, RA7, and RA9 and shunt resonators RA2, RA4, RA6, RA8, RAA, andRAAb. One or more of the shunt resonators RA2, RA4, RA6, RA8, RAA, andRAAb can have a plurality of resonant frequencies. The first filter 132also includes a series inductor L2 coupled between the plurality ofacoustic wave resonators and an RF port RF_OUT1. The first filter 132includes a shunt inductor LCuB3. In certain applications, the firstfilter 132 can have the frequency response shown in FIGS. 3C and 3D. Insuch applications, the shunt resonator RA2 can have two resonantfrequencies corresponding to the curve in FIG. 3D.

The second filter 134 includes a plurality of acoustic wave resonators.The acoustic wave resonators of the second filter 134 include seriesresonators RB1, RB2, and RB4, shunt resonators RB3 and RB5, and doublemode SAW (DMS) elements D4A and D4B. The shunt resonator RB3 and/or theshunt resonator RB4 can have a plurality of resonant frequencies inaccordance with any suitable principles and advantages disclosed hereinin certain embodiments. The second filter 134 also includes a seriesinductor L3 coupled between the plurality of acoustic wave resonatorsand an RF port RF_OUT2.

Acoustic wave resonators of the duplexer 130 can be TCSAW resonators.Such TCSAW resonators can have temperature compensation layers ofdifferent thicknesses. FIG. 13B is a schematic diagram of a crosssection of surface acoustic wave resonators of the duplexer 130 of FIG.13A according to an embodiment. As shown in FIG. 13B, an acoustic wavecomponent 135 includes TCSAW resonators 136A, 136B, and 136C. One ormore of the TCSAW resonators 136A, 136B, and 136C can have two or moreresonant frequencies in accordance with any suitable principles andadvantages disclosed herein. The acoustic wave component 135 includes apiezoelectric layer 137 and IDT electrodes 138A, 138B, and 138C on thepiezoelectric layer 137. A temperature compensation layer 139 ispositioned over the IDT electrodes 138A, 138B, and 138C and thepiezoelectric layer 137. The piezoelectric layer 137 can be a lithiumniobate layer. The temperature compensation layer 139 can be a silicondioxide layer.

The temperature compensation layer 139 has a plurality of differentthicknesses over respective IDT electrodes 138A, 138B, and 138C. Thetemperature compensation layer 139 being thicker can result in TCFcloser to zero and lower Q and electromechanical coupling coefficient(k²). The temperature compensation layer 139 can be have differentthicknesses such that certain resonators have TCF closer to zero andother resonators have higher Q and k². The first TCSAW resonator 136Ahas a first thickness H1 of the temperature compensation layer 139 overthe piezoelectric layer 137. The second TCSAW resonator 136B has asecond thickness H2 of the temperature compensation layer 139 over thepiezoelectric layer 137. The third TCSAW resonator 136C has a thirdthickness H3 of the temperature compensation layer 139 over thepiezoelectric layer 137. As shown in FIG. 13B, the third thickness H3 isgreater than the second thickness H2 and the second thickness H2 isgreater than the first thickness.

In an embodiment of the duplexer 130, acoustic wave resonators RA1, RB1,RB2, RB4 can be TCSAW resonators with the first thickness H1 like theTCSAW resonator 136A, acoustic wave resonators RA7, RA9, RB3, and RB5can be TCSAW resonators with the second thickness H2 like the TCSAWresonator 136B, and acoustic wave resonators RA2, RA3, RA4, RA5, RA6,RA8, RAA, and RAAb can be TCSAW resonators with the third thickness H3like the TCSAW resonator 136C.

FIG. 14A is a schematic diagram of a duplexer 140 that includes anacoustic wave filter according to an embodiment. The duplexer 140includes a first filter 142 and a second filter 144 coupled to togetherat a common node COM. One of the filters of the duplexer 140 can be atransmit filter and the other of the filters of the duplexer 140 can bea receive filter. The transmit filter and the receive filter can berespective ladder filters with acoustic wave resonators having atopology similar to the ladder filter 110 of FIG. 11 . In some otherinstances, such as in a diversity receive application, the duplexer 140can include two receive filters. The common node COM can be an antennanode.

The first filter 142 is an acoustic wave filter arranged to filter aradio frequency signal. The first filter 142 can include acoustic waveresonators coupled between a first radio frequency node RF1 and thecommon node. The first radio frequency node RF1 can be a transmit nodeor a receive node. The first filter 142 includes a shunt acoustic waveresonator having multiple resonant frequencies in accordance with anysuitable principles and advantages disclosed herein.

The second filter 144 can be any suitable filter arranged to filter asecond radio frequency signal. The second filter 144 can be, forexample, an acoustic wave filter, an acoustic wave filter that includesshunt resonator with multiple resonant frequencies, an LC filter, ahybrid acoustic wave LC filter, or the like. The second filter 144 iscoupled between a second radio frequency node RF2 and the common node.The second radio frequency node RF2 can be a transmit node or a receivenode

Although example embodiments may be discussed with filters or duplexersfor illustrative purposes, any suitable principles and advantagesdisclosed herein can be implement in a multiplexer that includes aplurality of filters coupled together at a common node. Examples ofmultiplexers include but are not limited to a duplexer with two filterscoupled together at a common node, a triplexer with three filterscoupled together at a common node, a quadplexer with four filterscoupled together at a common node, a hexaplexer with six filters coupledtogether at a common node, an octoplexer with eight filters coupledtogether at a common node, or the like. One or more filters of amultiplexer can include a shunt acoustic wave resonator having multipleresonant frequencies. Multiplexers include multiplexers with fixedmultiplexing and multiplexers with switched multiplexing.

FIG. 14B is a schematic diagram of a multiplexer 145 that includes anacoustic wave filter according to an embodiment. The multiplexer 145includes a plurality of filters 142 to 144 coupled together at a commonnode COM. The plurality of filters can include any suitable number offilters including, for example, 3 filters, 4 filters, 5 filters, 6filters, 7 filters, 8 filters, or more filters. Some or all of theplurality of acoustic wave filters can be acoustic wave filters.

The first filter 142 is an acoustic wave filter arranged to filter aradio frequency signal. The first filter 142 can include acoustic waveresonators coupled between a first radio frequency node RF1 and thecommon node. The first radio frequency node RF1 can be a transmit nodeor a receive node. The first filter 142 includes a shunt acoustic waveresonator having multiple resonant frequencies in accordance with anysuitable principles and advantages disclosed herein. The other filter(s)of the multiplexer 145 can include one or more acoustic wave filters,one or more acoustic wave filters that include a shunt resonator withmultiple resonant frequencies, one or more LC filters, one or morehybrid acoustic wave LC filters, or any suitable combination thereof.

The acoustic wave resonators with multiple resonant frequenciesdisclosed herein can be implemented in a variety of packaged modules.Some example packaged modules will now be disclosed in which anysuitable principles and advantages of the acoustic wave filters and/oracoustic wave resonators disclosed herein can be implemented. Theexample packaged modules can include a package that encloses theillustrated circuit elements. A module that includes a radio frequencycomponent can be referred to as a radio frequency module. Theillustrated circuit elements can be disposed on a common packagingsubstrate. The packaging substrate can be a laminate substrate, forexample. FIGS. 15 to 18 are schematic block diagrams of illustrativepackaged modules according to certain embodiments. Any suitablecombination of features of these packaged modules can be implementedwith each other. While duplexers are illustrated in the example packagedmodules of FIGS. 16 to 18 , any other suitable multiplexer that includesa plurality of filters coupled to a common node can be implementedinstead of one or more duplexers. For example, a quadplexer can beimplemented in certain applications. Alternatively or additionally, oneor more filters of a packaged module can be arranged as a transmitfilter or a receive filter that is not included in a multiplexer.

FIG. 15 is a schematic diagram of a radio frequency module 150 thatincludes an acoustic wave component 152 according to an embodiment. Theillustrated radio frequency module 150 includes the acoustic wavecomponent 152 and other circuitry 153. The acoustic wave component 152can include one or more acoustic wave in accordance with any suitablecombination of features of the acoustic wave filters and/or acousticwave resonators disclosed herein. The acoustic wave component 152 caninclude a SAW die that includes SAW resonators, for example.

The acoustic wave component 152 shown in FIG. 15 includes one or moreacoustic wave filters 154 and terminals 155A and 155B. The one or moreacoustic wave filters 154 includes an acoustic wave resonator havingmultiple resonant frequencies implemented in accordance with anysuitable principles and advantages disclosed herein. The terminals 155Aand 154B can serve, for example, as an input contact and an outputcontact. Although two terminals are illustrated, any suitable number ofterminals can be implemented for a particular application. The acousticwave component 152 and the other circuitry 153 are on a common packagingsubstrate 156 in FIG. 15 . The package substrate 156 can be a laminatesubstrate. The terminals 155A and 155B can be electrically connected tocontacts 157A and 157B, respectively, on the packaging substrate 156 byway of electrical connectors 158A and 158B, respectively. The electricalconnectors 158A and 158B can be bumps or wire bonds, for example.

The other circuitry 153 can include any suitable additional circuitry.For example, the other circuitry can include one or more poweramplifiers, one or more radio frequency switches, one or more additionalfilters, one or more low noise amplifiers, one or more RF couplers, oneor more delay lines, one or more phase shifters, the like, or anysuitable combination thereof. The other circuitry 153 can beelectrically connected to the one or more acoustic wave filters 154. Theradio frequency module 150 can include one or more packaging structuresto, for example, provide protection and/or facilitate easier handling ofthe radio frequency module 150. Such a packaging structure can includean overmold structure formed over the packaging substrate 156. Theovermold structure can encapsulate some or all of the components of theradio frequency module 150.

FIG. 16 is a schematic block diagram of a module 160 that includesduplexers 161A to 161N and an antenna switch 162. One or more filters ofthe duplexers 161A to 161N can include an acoustic wave resonator withtwo or more resonant frequencies in accordance with any suitableprinciples and advantages disclosed herein. Any suitable number ofduplexers 161A to 161N can be implemented. The antenna switch 162 canhave a number of throws corresponding to the number of duplexers 161A to161N. The antenna switch 162 can include one or more additional throwscoupled to one or more filters external to the module 160 and/or coupledto other circuitry. The antenna switch 162 can electrically couple aselected duplexer to an antenna port of the module 160.

FIG. 17 is a schematic block diagram of a module 170 that includes apower amplifier 176, a radio frequency switch 178, and duplexers 161A to161N according to an embodiment. The power amplifier 176 can amplify aradio frequency signal. The radio frequency switch 178 can be amulti-throw radio frequency switch. The radio frequency switch 178 canelectrically couple an output of the power amplifier 176 to a selectedtransmit filter of the duplexers 161A to 161N. One or more filters ofthe duplexers 161A to 161N can include any suitable number of acousticwave resonators that have a plurality of resonant frequencies inaccordance with any suitable principles and advantages disclosed herein.Any suitable number of duplexers 161A to 161N can be implemented.

FIG. 18 is a schematic diagram of a radio frequency module 180 thatincludes an acoustic wave filter according to an embodiment. Asillustrated, the radio frequency module 180 includes duplexers 161A to161N that include respective transmit filters 183A1 to 183N1 andrespective receive filters 183A2 to 183N2, a power amplifier 176, aselect switch 178, and an antenna switch 162. The radio frequency module180 can include a package that encloses the illustrated elements. Theillustrated elements can be disposed on a common packaging substrate187. The packaging substrate 187 can be a laminate substrate, forexample. A radio frequency module that includes a power amplifier can bereferred to as a power amplifier module. A radio frequency module caninclude a subset of the elements illustrated in FIG. 18 and/oradditional elements. The radio frequency module 180 may include any oneof the acoustic wave devices with a plurality of resonant frequencies inaccordance with any suitable principles and advantages disclosed herein.

The duplexers 161A to 161N can each include two acoustic wave filterscoupled to a common node. For example, the two acoustic wave filters canbe a transmit filter and a receive filter. As illustrated, the transmitfilter and the receive filter can each be a band pass filter arranged tofilter a radio frequency signal. One or more of the transmit filters183A1 to 183N1 can include an acoustic wave resonator with a pluralityof resonant frequencies in accordance with any suitable principles andadvantages disclosed herein. Similarly, one or more of the receivefilters 183A2 to 183N2 can include an acoustic wave resonator with aplurality of resonant frequencies in accordance with any suitableprinciples and advantages disclosed herein. Although FIG. 18 illustratesduplexers, any suitable principles and advantages disclosed herein canbe implemented in other multiplexers (e.g., quadplexers, hexaplexers,octoplexers, etc.) and/or in switch-plexers.

The power amplifier 176 can amplify a radio frequency signal. Theillustrated switch 178 is a multi-throw radio frequency switch. Theswitch 178 can electrically couple an output of the power amplifier 176to a selected transmit filter of the transmit filters 183A1 to 183N1. Insome instances, the switch 178 can electrically connect the output ofthe power amplifier 176 to more than one of the transmit filters 183A1to 183N1. The antenna switch 162 can selectively couple a signal fromone or more of the duplexers 161A to 161N to an antenna port ANT. Theduplexers 161A to 161N can be associated with different frequency bandsand/or different modes of operation (e.g., different power modes,different signaling modes, etc.).

The filters with an acoustic wave resonator having a plurality ofresonant frequencies disclosed herein can be implemented in a variety ofwireless communication devices. FIG. 19A is a schematic diagram of awireless communication device 190 that includes filters 193 in a radiofrequency front end 192 according to an embodiment. One or more of thefilters 193 can an acoustic wave resonator having a plurality ofresonant frequencies in accordance with any suitable principles andadvantages disclosed herein. The wireless communication device 190 canbe any suitable wireless communication device. For instance, a wirelesscommunication device 190 can be a mobile phone, such as a smart phone.As illustrated, the wireless communication device 190 includes anantenna 191, an RF front end 192, a transceiver 194, a processor 195, amemory 196, and a user interface 197. The antenna 191 can transmit RFsignals provided by the RF front end 192. Such RF signals can includecarrier aggregation signals. The antenna 191 can receive RF signals andprovide the received RF signals to the RF front end 192 for processing.Such RF signals can include carrier aggregation signals. The wirelesscommunication device 190 can include two or more antennas in certaininstances.

The RF front end 192 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplex filters, oneor more multiplexers, one or more frequency multiplexing circuits, thelike, or any suitable combination thereof. The RF front end 192 cantransmit and receive RF signals associated with any suitablecommunication standards. One or more of the filters 193 can include anacoustic wave resonator with a plurality of resonant frequencies thatincludes any suitable combination of features of the embodimentsdisclosed above.

The transceiver 194 can provide RF signals to the RF front end 192 foramplification and/or other processing. The transceiver 194 can alsoprocess an RF signal provided by a low noise amplifier of the RF frontend 192. The transceiver 194 is in communication with the processor 195.The processor 195 can be a baseband processor. The processor 195 canprovide any suitable base band processing functions for the wirelesscommunication device 190. The memory 196 can be accessed by theprocessor 195. The memory 196 can store any suitable data for thewireless communication device 190. The user interface 197 can be anysuitable user interface, such as a display with touch screencapabilities.

FIG. 19B is a schematic diagram of a wireless communication device 200that includes filters 193 in a radio frequency front end 192 and secondfilters 203 in a diversity receive module 202. The wirelesscommunication device 200 is like the wireless communication device 190of FIG. 19A, except that the wireless communication device 200 alsoincludes diversity receive features. As illustrated in FIG. 19B, thewireless communication device 200 includes a diversity antenna 201, adiversity module 202 configured to process signals received by thediversity antenna 201 and including filters 203, and a transceiver 194in communication with both the radio frequency front end 192 and thediversity receive module 202. One or more of the second filters 203 caninclude an acoustic wave resonator having a plurality of resonantfrequencies in accordance with any suitable principles and advantagesdisclosed herein.

Any of the embodiments described above can be implemented in associationwith mobile devices such as cellular handsets. The principles andadvantages of the embodiments can be used for any systems or apparatus,such as any uplink wireless communication device, that could benefitfrom any of the embodiments described herein. The teachings herein areapplicable to a variety of systems. Although this disclosure includesexample embodiments, the teachings described herein can be applied to avariety of structures. Any of the principles and advantages discussedherein can be implemented in association with RF circuits configured toprocess signals having a frequency in a range from about 30 kHz to 300GHz, such as in a frequency range from about 400 MHz to 8.5 GHz.Acoustic wave filters disclosed herein can filter RF signals atfrequencies up to and including millimeter wave frequencies.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as packaged radio frequency modules, uplinkwireless communication devices, wireless communication infrastructure,electronic test equipment, etc. Examples of the electronic devices caninclude, but are not limited to, a mobile phone such as a smart phone, awearable computing device such as a smart watch or an ear piece, atelephone, a television, a computer monitor, a computer, a modem, ahand-held computer, a laptop computer, a tablet computer, a microwave, arefrigerator, a vehicular electronics system such as an automotiveelectronics system, a robot such as an industrial robot, an Internet ofthings device, a stereo system, a digital music player, a radio, acamera such as a digital camera, a portable memory chip, a homeappliance such as a washer or a dryer, a peripheral device, a wristwatch, a clock, etc. Further, the electronic devices can includeunfinished products.

Unless the context indicates otherwise, throughout the description andthe claims, the words “comprise,” “comprising,” “include,” “including”and the like are to generally be construed in an inclusive sense, asopposed to an exclusive or exhaustive sense; that is to say, in thesense of “including, but not limited to.” Conditional language usedherein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,”“for example,” “such as” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. The word “coupled”, as generally used herein, refers to two ormore elements that may be either directly connected, or connected by wayof one or more intermediate elements. Likewise, the word “connected”, asgenerally used herein, refers to two or more elements that may be eitherdirectly connected, or connected by way of one or more intermediateelements. Additionally, the words “herein,” “above,” “below,” and wordsof similar import, when used in this application, shall refer to thisapplication as a whole and not to any particular portions of thisapplication. Where the context permits, words in the above DetailedDescription using the singular or plural number may also include theplural or singular number respectively.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel resonators, filters,multiplexer, devices, modules, wireless communication devices,apparatus, methods, and systems described herein may be embodied in avariety of other forms. Furthermore, various omissions, substitutionsand changes in the form of the resonators, filters, multiplexer,devices, modules, wireless communication devices, apparatus, methods,and systems described herein may be made without departing from thespirit of the disclosure. For example, while blocks are presented in agiven arrangement, alternative embodiments may perform similarfunctionalities with different components and/or circuit topologies, andsome blocks may be deleted, moved, added, subdivided, combined, and/ormodified. Each of these blocks may be implemented in a variety ofdifferent ways. Any suitable combination of the elements and/or acts ofthe various embodiments described above can be combined to providefurther embodiments. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the disclosure.

What is claimed is:
 1. An acoustic wave resonator with a plurality of resonant frequencies, the acoustic wave resonator comprising: a piezoelectric layer; and an interdigital transducer electrode on the piezoelectric layer, the interdigital transducer electrode including first interdigital transducer electrode fingers and second interdigital transducer electrode fingers, the first interdigital transducer electrode fingers having a first pitch corresponding to a first resonant frequency, and the second interdigital transducer electrode fingers having a second pitch corresponding to a second resonant frequency.
 2. The acoustic wave resonator of claim 1 wherein the second resonant frequency is between the first resonant frequency and an edge of a pass band of an acoustic wave filter that includes the acoustic wave resonator.
 3. The acoustic wave resonator of claim 1 wherein the acoustic wave resonator is configured to generate a surface acoustic wave.
 4. The acoustic wave resonator of claim 1 further comprising a temperature compensation layer over the interdigital transducer electrode.
 5. The acoustic wave resonator of claim 4 wherein the temperature compensation layer is a silicon dioxide layer.
 6. The acoustic wave resonator of claim 1 further comprising a support substrate, the piezoelectric layer being positioned on the support substrate.
 7. The acoustic wave resonator of claim 1 wherein the acoustic wave resonator is configured to generate a boundary acoustic wave.
 8. The acoustic wave resonator of claim 1 wherein the acoustic wave resonator is configured to generate a Lamb wave.
 9. The acoustic wave resonator of claim 1 wherein the interdigital transducer electrode includes third interdigital transducer electrode fingers having a third pitch corresponding to a third resonant frequency.
 10. The acoustic wave resonator of claim 1 wherein the second resonant frequency is at least 5 megahertz above the first resonant frequency.
 11. The acoustic wave resonator of claim 1 wherein the piezoelectric layer is an aluminum nitride layer.
 12. The acoustic wave resonator of claim 1 wherein the interdigital transducer electrode includes a bus bar from which both the first interdigital transducer electrode fingers and the second interdigital transducer electrode fingers extend, and the interdigital transducer electrode is positioned between two acoustic reflectors that are on the piezoelectric layer.
 13. A multiplexer with filters for filter radio frequency signals, the multiplexer comprising: a first filter including an acoustic wave resonator, the acoustic wave resonator including a piezoelectric layer and an interdigital transducer electrode on the piezoelectric layer, the interdigital transducer electrode including first interdigital transducer electrode fingers and second interdigital transducer electrode fingers, the first interdigital transducer electrode fingers having a first pitch corresponding to a first resonant frequency, and the second interdigital transducer electrode fingers having a second pitch corresponding to a second resonant frequency; and a second filter coupled to the first filter at a common node, the second filter configured to filter a second radio frequency signal.
 14. The multiplexer of claim 13 wherein the second filter includes acoustic wave resonators.
 15. The multiplexer of claim 13 further comprising: a third filter coupled to the common node, the third filter configured to filter a third radio frequency signal; and a fourth filter coupled to the common node, the fourth filter configured to filter a fourth radio frequency signal.
 16. The multiplexer of claim 15 wherein each of the second filter, the third filter, and the fourth filter is an acoustic wave filter.
 17. The multiplexer of claim 13 wherein the multiplexer is configured to provide filtering for at least two carriers of a carrier aggregation.
 18. A method of filtering a radio frequency signal with an acoustic wave filter, the method comprising: receiving, by the acoustic wave filter, a radio frequency signal; and generating, with an acoustic wave resonator of the acoustic wave filter that includes an interdigital transducer electrode including first interdigital transducer electrode fingers having a first pitch and second interdigital transducer electrode fingers having a second pitch, two notches in a frequency response of the acoustic wave resonator corresponding to the first pitch and the second pitch to thereby improve rejection of the acoustic wave filter.
 19. The method of claim 18 wherein the acoustic wave resonator having at least first and second resonant frequencies, the second resonant frequency is between the first resonant frequency and an edge of a pass band of the acoustic wave filter.
 20. The method of claim 18 wherein the acoustic wave resonator is configured to generate a boundary acoustic wave. 